There have been known semiconductor devices manufactured by: producing a substrate for semiconductor element mount by forming a resist mask carrying a particular pattern on one side of base material having electroconductivity, plating the base material, where uncovered with the resist mask, with electroconductive metal, to form a metal layer for mounting a semiconductor element thereon and an electrode layer for connection with externals, and removing the resist mask; mounting a semiconductor element on the metal layer region of the substrate for semiconductor element mount; wire-bonding and then resin-sealing the semiconductor element and the electrode layer; and removing the base material, so that the metal layer and the electrode layer are left uncovered on the resin side.
Such semiconductor devices used to be conventionally made of metal base material of 0.1-0.25 mm thickness called leadframe. However, in place of the conventional metal base material, use of a metal layer and an electrode layer of 0.01-0.08 mm thickness formed by plating facilitates thinner design of products. In this case, while the base material used in the processes of production is removed, it is important that the metal layer and the electrode layer formed by plating should be firmly adhered to the sealing resin and remain, unremoved, on the resin side.
Patent Document 1 states that a substrate for semiconductor element mount having a hangover portion beyond the upper side rim of a metal layer and an electrode layer is obtained by electrodeposition (plating) of electroconductive metal over the formed resist mask, so that the metal layer and the electrode layer firmly remain on the resin side with the hangover portion biting into the resin in resin-sealing.
Patent Document 2 states forming of a metal layer or an electrode layer having a trapezoidal sectional shape with the top base longer than the bottombase, by shaping a resist mask trapezoidal using scattered ultraviolet light.